Drug X causes an increase in blood pressure and a decrease in heart rate when administered to a patient intravenously. If an antagonist at ganglionic nicotinic receptors is administered first, drug X causes an increase in blood pressure and an increase in heart rate. Drug X most likely is

Correct Answer: B

Rationale: The correct answer is B: Norepinephrine. When an antagonist at ganglionic nicotinic receptors is administered, it blocks the inhibitory effect on sympathetic tone. Since norepinephrine is a sympathetic neurotransmitter that increases blood pressure and heart rate, it is likely that Drug X is norepinephrine. Propranolol (A) is a beta-blocker that decreases heart rate, Isoproterenol (C) is a beta-agonist that increases heart rate, and Terbutaline (D) is a beta-agonist that also increases heart rate. These choices do not align with the observed effects of Drug X when the ganglionic nicotinic receptor antagonist is administered.

Correct Answer: D

Rationale: The correct answer is D: Hydrolysis by cholinesterase enzyme. Acetylcholine is broken down by cholinesterase enzyme into choline and acetate, leading to the termination of its action. Rapid hepatic metabolism (A) is not the primary mechanism for acetylcholine breakdown. Reuptake by nerve endings (B) refers to reuptake of neurotransmitters, not breakdown. Binding to plasma proteins (C) does not affect the duration of acetylcholine action.

Correct Answer: D

Rationale: Hyoscine, also known as scopolamine, is an anticholinergic drug that acts by blocking muscarinic receptors. It produces sedation by crossing the blood-brain barrier and affecting the central nervous system. Its antiemetic action is due to its ability to inhibit the vomiting center in the brain. Stimulation of the respiratory center is not a typical action of hyoscine. Lastly, hyoscine decreases salivary secretion due to its anticholinergic effects. Therefore, the correct answer is D (Increase of salivary secretion) as it is inconsistent with the pharmacological actions of hyoscine.

Correct Answer: A

Rationale: The correct answer is A: Eating seeds containing atropine. Atropine is a plant alkaloid commonly found in certain seeds that can cause symptoms such as fever, skin flush, dry mouth, constipation, dilated pupils, and increased heart rate when ingested. Atropine is known to have anticholinergic effects, which align with the symptoms presented by the child. Malathion (B) is an insecticide that typically causes different symptoms like nausea, vomiting, and diarrhea. Echothiophate drops (C) are cholinesterase inhibitors used in the treatment of glaucoma, which would not produce the described symptoms. Physostigmine (D) is a cholinesterase inhibitor that would not cause symptoms of anticholinergic toxicity seen in the child.

Correct Answer: B

Rationale: The correct answer is B: Carbachol. Anti-cholinesterase drugs inhibit the enzyme acetylcholinesterase, increasing levels of acetylcholine. Carbachol is a direct cholinergic agonist, not an anti-cholinesterase drug. Physostigmine, Metrifonate, and Neostigmine are all anti-cholinesterase drugs that work by inhibiting acetylcholinesterase. Physostigmine is used for glaucoma and atropine overdose, Metrifonate for parasitic infections, and Neostigmine for myasthenia gravis.